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Atrial fibrillation is a very common heart rhythm disorder which is caused by a rhythm disturbance of the atria and results in irregular, chaotic, ventricular waveforms varying from slow to extremely rapid heart beating.

During atrial fibrillation, the heart's two small upper chambers called the atria, quiver instead of beating effectively. That’s why blood isn't pumped out of them completely so it may pool and clot. If a piece of a blood clot in the atria leaves the heart and becomes lodged in an artery in the brain, it can lead to a stroke.

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Incidence

Atrial fibrillation is the most common cardiac arrhythmia. More than 2 million Americans have this condition, which can cause palpitations, shortness of breath, fatigue and a stroke. The condition is increasingly common with advancing age. It affects less than 1 percent of Americans younger than 60, but as many as one in 10 people older than 80. Overall, approximately 15-25% of all the strokes in the United States can be attributed to atrial fibrillation.

Risk factors

Known risk factors include:

  • male sex
  • valvular heart disease
  • rheumatic valvular disease
  • CHF
  • hypertension
  • diabetes

Additional risk factors, such as advanced age and prior history of stroke, place patients with preexisting atrial fibrillation at even higher risk for further complications such as stroke.

Signs and symptoms of atrial fibrillation

It is clear that a heart in atrial fibrillation simply doesn't beat efficiently which means that it may not be able to pump an adequate amount of blood which leads to a drop in blood pressure.

People with atrial fibrillation experience:

  • Palpitations, which are sensations of a racing, uncomfortable, irregular heartbeat or a flopping in your chest
  • Weakness
  • Lightheadedness
  • Shortness of breath
  • Chest pain

However, some people with atrial fibrillation have no symptoms and are unaware of their condition until their doctor discovers it during some regular physical examination.

Normal anatomy of the heart and mechanism of the condition

A heart normally consists of four chambers, two upper chambers called atria and two lower chambers called ventricles. Within the upper right chamber there is a specific group of cells called the sinus node which represent a natural heart's pacemaker. The sinus node produces the impulse that starts each heartbeat. During a normal rhythm, the impulse travels first through the atria, then through a connecting pathway between the upper and lower chambers called the atrioventricular node.
What happens in atrial fibrillation? In atrial fibrillation, the atria are affected by chaotic electrical signals. As a result, they quiver. Another result is that the ventricles also beat rapidly, but not as rapidly as the atria. This leads to the irregular and fast heart rhythm that affects both atria and ventricles. The heart rate in atrial fibrillation may range from 100 to 175 beats a minute. The normal range for a heart rate is 60 to 100 beats a minute.

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